265 lines
8.6 KiB
Java
265 lines
8.6 KiB
Java
/* This file is based on something from Apache's Xalan-J 2.4.0. As is
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our right, we have licensed it under the THDL Open Community
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License. We list the THDL as the "Initial Developer", because
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Apache doesn't want e-mail about this code. But colloquially, one
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would say that Apache is the first developer. */
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/*
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The contents of this file are subject to the THDL Open Community License
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Version 1.0 (the "License"); you may not use this file except in compliance
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with the License. You may obtain a copy of the License on the THDL web site
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(http://www.thdl.org/).
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Software distributed under the License is distributed on an "AS IS" basis,
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WITHOUT WARRANTY OF ANY KIND, either express or implied. See the
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License for the specific terms governing rights and limitations under the
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License.
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The Initial Developer of this software is the Tibetan and Himalayan Digital
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Library (THDL). Portions created by the THDL are Copyright 2001 THDL.
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All Rights Reserved.
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Contributor(s): ______________________________________.
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*/
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/*
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* The Apache Software License, Version 1.1
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*
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*
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* Copyright (c) 1999 The Apache Software Foundation. All rights
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* reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* 3. The end-user documentation included with the redistribution,
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* if any, must include the following acknowledgment:
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* "This product includes software developed by the
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* Apache Software Foundation (http://www.apache.org/)."
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* Alternately, this acknowledgment may appear in the software itself,
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* if and wherever such third-party acknowledgments normally appear.
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*
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* 4. The names "Xalan" and "Apache Software Foundation" must
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* not be used to endorse or promote products derived from this
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* software without prior written permission. For written
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* permission, please contact apache@apache.org.
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*
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* 5. Products derived from this software may not be called "Apache",
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* nor may "Apache" appear in their name, without prior written
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* permission of the Apache Software Foundation.
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*
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
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* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
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* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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* ====================================================================
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*
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* This software consists of voluntary contributions made by many
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* individuals on behalf of the Apache Software Foundation and was
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* originally based on software copyright (c) 1999, Lotus
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* Development Corporation., http://www.lotus.com. For more
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* information on the Apache Software Foundation, please see
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* <http://www.apache.org/>.
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*/
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package org.thdl.util;
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/**
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* A digital search trie for 7-bit ASCII text. The API is a subset of
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* java.util.Hashtable. The key must be a 7-bit ASCII string. The
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* value may be any Java Object. */
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public class Trie
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{
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/** Size of the m_nextChar array. */
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public static final int ALPHA_SIZE = 128;
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/** The root node of the tree. */
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Node m_Root;
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/**
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* Constructs a trie.
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*/
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public Trie()
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{
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m_Root = new Node();
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}
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private static final boolean caseInsensitive = false;
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/**
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* Puts an object into the trie for lookup.
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*
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* @param key must be a 7-bit ASCII string
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* @param value any java object, but not null.
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*
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* @return The old object that matched key, or null.
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* @throws NullPointerException if value is null or if key is null
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*/
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public Object put(String key, Object value)
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{
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if (null == value) throw new NullPointerException();
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final int len = key.length();
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Node node = m_Root;
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for (int i = 0; i < len; i++)
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{
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Node nextNode
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= node.m_nextChar[(caseInsensitive
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? Character.toUpperCase(key.charAt(i))
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: key.charAt(i))];
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if (nextNode != null)
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{
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node = nextNode;
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}
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else
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{
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for (; i < len; i++)
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{
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Node newNode = new Node();
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node.m_nextChar[(caseInsensitive
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? Character.toUpperCase(key.charAt(i))
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: key.charAt(i))] = newNode;
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node.m_isLeaf = false;
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node = newNode;
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}
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break;
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}
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}
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Object ret = node.m_Value;
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node.m_Value = value;
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return ret;
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}
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/**
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* Gets an object that matches the key.
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*
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* @param key must be a 7-bit ASCII string
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*
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* @return The object that matches the key, or null.
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*/
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public Object get(String key)
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{
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final int len = key.length();
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Node node = m_Root;
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for (int i = 0; i < len; i++)
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{
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try
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{
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node = node.m_nextChar[(caseInsensitive
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? Character.toUpperCase(key.charAt(i))
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: key.charAt(i))];
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}
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catch (ArrayIndexOutOfBoundsException e)
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{
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// the key is not 7-bit ASCII so we won't find it here
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node = null;
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ThdlDebug.noteIffyCode();
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}
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if (node == null)
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return null;
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}
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return node.m_Value;
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}
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/**
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* Returns true if and only if key is a prefix of another, distinct
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* member of the trie. Note that key may be in the trie as well as
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* a prefix of something in the trie, but not all keys in the trie
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* are prefixes of other keys. (In the trie you might naturally
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* construct for the extended Wylie keyboard, "t" is a prefix, as is
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* "ts", but "tsh", though a member of the trie, is not a prefix
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* because there is no string x such that x begins with "tsh" but is
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* not equal to "tsh" that is in the trie.)
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*
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* @param key must be a 7-bit ASCII string
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*
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* @return The object that matches the key, or null. */
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public boolean hasPrefix(String key)
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{
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final int len = key.length();
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Node node = m_Root;
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for (int i = 0; i < len; i++)
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{
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try
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{
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node = node.m_nextChar[(caseInsensitive
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? Character.toUpperCase(key.charAt(i))
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: key.charAt(i))];
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}
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catch (ArrayIndexOutOfBoundsException e)
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{
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// the key is not 7-bit ASCII so we won't find it here
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node = null;
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}
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if (node == null)
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return false;
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}
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return !node.m_isLeaf;
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}
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/**
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* The node representation for the trie.
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*/
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class Node
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{
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/**
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* Constructor, creates a Node[ALPHA_SIZE].
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*/
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Node()
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{
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m_nextChar = new Node[ALPHA_SIZE];
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m_Value = null;
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m_isLeaf = true;
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}
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/** The next nodes. */
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Node m_nextChar[];
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/** The value. */
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Object m_Value;
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/** True if and only if this node has no children. */
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boolean m_isLeaf;
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}
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}
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